With spring comes the greening of lawns and gardens — and, by extension, the greening of rivers, streams and other bodies of water. The first is a good thing. The second — well, that’s decidedly bad. As we finally dust off the winter doldrums and head outside to start gardening, it’s easy to…

A University of Washington study of 36 lakes has found evidence of nitrogen from human activities in more than 75 percent of them. Some of the lakes, which range from the U.S. Rocky Mountains to northern Europe, are “thousands of miles from the nearest city, industrial area or farm.” And the pollution dates back to before the…